Ion beam implanters are widely used in the process of doping workpieces. An ion beam implanter generates an ion beam comprised of desired species of positively charged ions. The ion beam impinges upon an exposed surface of a workpiece such as a semiconductor wafer, substrate or flat panel, thereby “doping” or implanting the workpiece surface with desired ions. Some ion implanters utilize serial implantation wherein a single wafer workpiece is positioned on a support in an implantation chamber and implanted. The implantation occurs one workpiece at a time. The support is oriented such that the workpiece is in front of the ion beam and is scanned to implant a desired dosage of ions. When the implantation is complete, the workpiece is removed from the support and another workpiece is positioned on the support for implantation.
In recent years, the trend in the semiconductor industry has been to use increasingly larger wafer workpieces, for example, 300 mm. diameter wafers. The ability to implant large wafer workpieces or other workpieces such as flat panels serially has become very desirable. One way to implant a workpiece serially is to move it within an evacuated process or implantation chamber in front of a scanned or broad ion beam. U.S. Pat. No. 6,710,360 B2 to Ferrara, assigned to the assignee of the present invention, discloses a workpiece support structure that provides: a rotation member rotatably affixed to process chamber for changing an implantation angle of the workpiece with respect to the ion beam within the process chamber and a translation member movably coupled to the rotation member and supporting the workpiece for linear movement along a path of travel. The translation member moves the workpiece along a direction of movement such that, for any desired implantation angle, a distance traversed by ion beam within the implantation chamber before striking the implantation surface of the workpiece is substantially constant.
One issue with regard to the translation member is that of contamination. If the translation member is housed within or is in fluid communication with the evacuated implantation chamber, dopant and photoresist material dislodged from a workpiece during implantation tend to coat the translation member components causing early failure of the translation member. Of even greater importance are particulates which may be deposited on the workpiece being implanted. If the translation member and associate harnessing are within the implantation chamber or are in fluid communication with the implantation chamber, particulates emitted by these components during linear movement of the translation member may be deposited on the workpiece thereby contaminating it. Since even minute amounts of particulate matter on a workpiece may cause a workpiece to be rejected, workpiece contamination is of paramount importance.
What is desired is a workpiece support structure that effectively isolates the translation member from the implantation chamber evacuated interior region.